1. Field of the Invention
The present invention relates to a plural pressure oil energies selective recovery apparatus which can selectively recover energy stored in each of plural hydraulic actuators based upon recovery conditions for preferentially recovering the energy.
2. Description of the Related Art
In general, a return pressure oil from a hydraulic actuator is directly returned to a tank. Since an energy of the return pressure oil is converted into a thermal energy via a throttle valve or the like provided in a return circuit to the tank and directly discharged to the outside, the energy of the return pressure oil has never been reutilized. Consequently, it has been attempted to recover and reutilize the energy of the return pressure oil of the hydraulic actuator. As a recovery apparatus for this purpose, for example, JP-A-10-184615 filed by the applicant of this application proposes a return pressure oil recovery apparatus.
In the pressure oil recovery apparatus, a return pressure oil is selected out of return pressure oils from plural hydraulic actuators according to an instruction from an operation instructor, and an energy of the selected return pressure oil is recovered and reutilized. As shown in FIG. 7, this return pressure oil recovery apparatus, by a selection circuit 54 controlled by an external operation instruction, selectively controls communication of one or two sub-recovery circuits among sub-recovery circuits 53a to 53d, which pass return pressure oils from plural hydraulic actuators 50 to 52, with a main recovery circuit 55 connected to a first hydraulic pump motor 56 serving as a recovery unit and supplies pressure oils passing through the sub-recovery circuits communicating with the main recovery circuit 55 to a first hydraulic pump motor 56, thereby causing the first hydraulic pump motor 56 to perform motor actions. A second hydraulic pump motor 57 mechanically communicating with the first hydraulic pump motor 56 performs a pump action by the driving of the first hydraulic pump motor 56, and a high pressure oil discharged from the second hydraulic pressure pump motor 57 is stored in an accumulator 58.
Next, the return pressure oil recovery apparatus supplies the high pressure oil stored in the accumulator 58 to the second hydraulic pump motor 57, thereby causing the second hydraulic pump motor 57 to perform the motor action, and the first hydraulic pump motor 56 performs the pump action by the driving of the second hydraulic pump motor 57. The pressure oil discharged from the first hydraulic pump motor 56 merges with a pressure oil from a hydraulic pump 60 via a check valve 59 and reutilized.
In the above-mentioned return pressure oil recovery apparatus, recovery work of a pressure oil is performed by selecting a return pressure oil out of return pressure oils from the plural hydraulic actuators with the selection circuit and supplying a pressure oil from a desired hydraulic actuator to the first hydraulic pump motor 56 serving as a recovery unit. Moreover, the recovery work is performed in accordance with a priority determined in advance which defines a return pressure oil from a hydraulic actuator of which work machine is to be recovered preferentially. Selective control of communication between the sub-recovery circuits 53a to 53d and the main recovery circuit 55 is performed in accordance with the priority by an instruction from an operation instructor, and a hydraulic actuator from which a return pressure oil is to be recovered can be determined. Consequently, since the hydraulic actuator from which are turn pressure oil is to be recovered can be selected in accordance with the priority decided in advance in response to the operation instruction, control becomes easy and a recovery efficiency can be increased. Thus, a recovery efficiency as a whole in every work can be increased.
However, in the above-mentioned return pressure oil recovery apparatus, the priority determined in advance is simply set such that the recovery efficiency of a return pressure oil is increased, and a specific method of determining a priority is not specifically disclosed.